The present invention relates generally to communication networks, and more specifically, to upgrading circuits in an optical network in a non-service affecting manner.
Today, SONET/SDH is the predominant technology for transport in worldwide public carrier networks. One of the key attributes of SONET/SDH is its ability to provide network survivability in point-to-point, ring, and mesh architectures. Many networks today are based upon fiber-ring architectures, as evidenced by the proliferation of SONET/SDH rings all the way from the long-haul backbone to the metropolitan and regional areas. Ring topologies are important because SONET uses it for protection purposes. Network operators have become accustomed to the fast, timely recovery capabilities provided by SONET/SDH automatic protection switching (APS) schemes, such as unidirectional path switched rings (UPSR)/sub-network connection protection (SNCP), 1+1 and bi-directional line switched rings (BLSR).
UPSR is a closed-loop, transport architecture that protects against fiber cuts and node failures by providing duplicate, geographically diverse paths for each circuit. A UPSR network is composed of two counter rotating fiber rings; referred to as the working and protection rings. Adjacent nodes on the ring are connected by a single pair of optical fibers, which form the two counter rotating rings carrying traffic in opposite directions. Working traffic is sent on the working ring in one direction on one fiber and copies are transmitted on the protection ring in the opposite direction over the other fiber. A destination node in the ring receives two signals, one along each ring. The node monitors transmission on both fibers and performs a protection switch to the alternate path if it detects degraded transmission. In this way, when there is a single link failure, it can recover by switching to the available signal. The UPSR is simpler than the two-fiber (2F) or four-fiber (4F) BLSRs since it requires only two fibers to operate.
A 2F-BLSR network also has two counter rotating fiber rings. Each fiber pair between two nodes is a full-duplex link. In this link, half the bandwidth carries working traffic, and the other half is for protection. If there is a single link failure, the working traffic that was carried on the link is looped back around the ring using the protection bandwidth of the other links. A 4F-BLSR network is similar to the 2F-BLSR except that there are two pairs of counter rotating fiber rings. One pair is used for working traffic and the other is used for protection.
It is often desired to upgrade an unprotected optical circuit to a path protected optical circuit, or upgrade a UPSR to a BLSR. Topology upgrade of circuits involves various steps at a number of nodes in the network. Conventional systems for upgrading an optical circuit use a set of time consuming and labor intensive manual steps which may require a technician to be present at each location. Conventional methods for upgrading circuits require, for example, use of TL1 (Transaction Language 1) and involve a piecemeal upgrade of the circuit at each node. Another drawback to these conventional topology upgrade techniques is that they do not provide a network view of the circuit during the upgrade. Thus, the user has to remember each step, perform manual checks at each step, and manually perform each step on each node.
There is, therefore, a need for a method and system for providing automatic in-service circuit upgrades. It is desirable that the method and system allow for the circuit or topology of a live network to be modified or converted without losing traffic on existing circuits.